1. Field of the Invention
The present invention relates to a high-voltage variable resistor for adjustment of focusing voltages and screen-grid voltages in television receivers, and other suitable apparatuses.
2. Description of the Related Art
A conventional high-voltage variable resistor includes a variable resistance board having a variable resistor portion and a fixed-resistance board having a fixed-resistance portion of bleeder resistors, etc., disposed thereon and a housing containing the same. See, for example, Japanese Unexamined Patent Application Publication No. 11-121212. This high-voltage variable resistor is provided with an insulating case that has one surface which is open, a panel wall in the shape of an xe2x80x9cLxe2x80x9d is provided inside the case, a first housing portion and a second housing portion which are divided by the panel wall are provided, a rectangular flat variable resistance board, on the surface of which a resistance pattern containing an arc-shaped variable resistor portion is disposed, is housed in the first housing portion, and a rectangular flat fixed-resistance board having longer and shorter sides, on the surface of which a fixed-resistance pattern is formed, and a high-voltage capacitor are housed in the second housing portion.
The variable resistance board is disposed such that its front surface faces the bottom surface of the case, and the rear side is filled with an insulation resin. The fixed-resistance board is arranged such that its shorter side extends from the bottom surface to the opening surface side of the case and that its longer side is parallel to the opening surface and the bottom surface of the case. In this high-voltage variable resistor, the second housing portion is constructed to surround the first housing portion so that the longer side of the fixed-resistance board is effectively disposed in the case. The thus constructed high-voltage variable resistor joined to a fly-back transformer (hereinafter referred to as an FBT) is put in the case, and the whole area on the side of the opening surface of the case is filled with the same resin as in the FBT.
As described above, in the conventional high-voltage variable resistor, the fixed-resistance board is disposed such that its longer side is parallel to the opening surface of the case, and it is necessary to provide an area in a top view when looked at from the opening surface of the case such that the longer side of the fixed-resistance board can be housed inside the case. As a result, the size of the case in a top view when looked at from the opening surface is restricted by the dimension of the longer side of the fixed-resistance board, and it is very difficult to reduce the size of the case. That is, since it is required to set the size of the case in accordance with the dimension of the longer side of the fixed-resistance board, miniaturization of the case, that is, miniaturization of the high-voltage variable resistor is prevented.
In order to overcome the problems described above, preferred embodiments of the present invention provide a high-voltage variable resistor that has a greatly reduced size achieved by disposing a fixed-resistance board such that its longer side extends from the bottom surface to the opening surface of a case.
According to a preferred embodiment of the present invention, a high-voltage variable resistor includes a variable resistance board having a resistance pattern including a variable resistor disposed thereon, a substantially rectangular flat fixed-resistance board having longer and shorter sides and a fixed-resistance pattern disposed thereon, and a case having an opening at one surface thereof. In the high-voltage variable resistor, the variable resistance board and the fixed-resistance board are housed in the case, and the fixed-resistance board is arranged such that the longer side of the fixed-resistance board extends from the bottom surface to the opening surface of the case.
According to the unique construction and arrangement of this preferred embodiment, since the fixed-resistance board is arranged such that the shorter side of the fixed-resistance board can be housed inside the case and, without the dimension of the longer side of the fixed-resistance board being restricted, the side of the case can be set in accordance with the dimension of the shorter side of the fixed-resistance board. As a result, the case can be made smaller as compared with conventional device. That is, it is enough to acquire an area in a top view of the case when looked at from the opening surface of the case such that the shorter side of the fixed-resistance board can be housed in the case. Furthermore, since the arrangement of the elements inside the case can be determined in accordance with the dimension of the shorter side of the fixed-resistance board, the case can be much smaller than conventional ones.
Furthermore, because of such miniaturization, the material cost of the case is greatly reduced, and the amount of resin to be used at the connection location of the high-voltage variable resistor to the FBT can be also reduced, and accordingly the cost reduction of the high-voltage variable resistor is further achieved.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.